Massachusetts students return to school after teacher killing

Students at Danvers High School in Massachusetts return to school Friday, Oct. 25, 2013, two days after a popular math teacher was killed.

October 25, 2013 12:00:00 AM PDT

DANVERS, Mass. --

Students at Danvers High School in Massachusetts are back in school Friday, two days after a popular math teacher was killed.

A U.S. flag outside the school flew at half-staff, and pink ribbons hung from a row of six trees in front of the building. An electronic sign displayed a tweet that the slain teacher had posted: "No matter what happens in life, be good to people. Being good to people is a wonderful legacy to leave behind."

Authorities still have not revealed how 24-year-old math teacher, Colleen Ritzer, was killed. One of her students, 14-year-old Philip Chism, has been charged with murder.

Police and school officials held a meeting Thursday night with parents, insisting they will take extra safety measures to reassure students.

The victim's family is asking for privacy as they arrange the funeral.

A motive remains unknown in the killing. Tuesday's school day ended for both Chism and Ritzer in her last-period Algebra I class, where she noticed him drawing in a notebook rather than taking notes, according to student Rania Rhaddaoui, who sat two seats from Chism.

Ritzer asked Chism to stay after class, Rhaddaoui said. She never returned home after that. Blood in a second-floor school bathroom helped lead investigators to her body, which was dumped in the woods behind the school.

Law enforcement sources tell ABC News that Chism followed Ritzer into the women's bathroom, killing her with a box cutter. He then allegedly put her body in a large recycling bin and moved her to the woods, the whole time captured on camera wearing a hat and gloves.